Shape Form propulsion

            The development of smart materials that could deform and contract in response to signals or the environment led to new ways in which vehicles could move about in their environment. One particularly successful adaptation of these new materials was in marine vehicles, which could through the use of these ‘artificial muscles’ (also known as electro-active polymers) mimic the motions of aquatic animals. This bio-mimetic propulsion started a new era in marine technology, because the movements they were copying were the result of millions of years of evolution these types of drive system were greatly more efficient, and were far less noisy than other methods. The military had particular interest in these technological applications, as marine craft could be active yet were all but silent to any hydrophone. This form of propulsion also greatly expanded the speed ranges capable underwater, and even small vehicles could travel at exceptionally fast speeds. Though the military had a great use for these propulsion systems, scientists were also using them to investigate the depths, the efficiency of these craft meant that power consumption was small, and the smooth motions and minimal disturbance of the water led to better instrument recordings.

            The use of smart materials has undergone further evolution inside Federation history, and although marine transport and warfare are pretty much obsolete the need to explore the sea has not, so these forms of propulsion live on in new vehicles. The early problems with these technologies were that the volume of ‘mobile hull’ was quite large, not just the elastic surface but also the banks of artificial muscle underneath. In science vessels this was not a major problem as most of the craft were originally unmanned, and so it was acceptable for the craft to predominantly be made from the smart materials. For manned ships a compromise had to be made, the crew require pressurised (in most cases) working environment, which is a pressurised metal container, as this was rigid the propulsive apparatus had to be built on the side of this. The best compromise, which is still use today is the use of propulsive vanes that run the length of the vessel. When in operation these vanes produce rhythmical waves which forces the vehicle through the water, the motions are themselves another copy from existing marine life. The vane technique requires only a small volume of flexible material, but still enough to achieve moderate accelerations, the other advantage to these parallel vanes is that with computer control and inertial sensing the craft can be made to hover in the marine environment or perform more nimble manoeuvring.

A diagram of a linear array of vane elements

            The predominant changes to the materials used for propulsion are only really apparent at the extremes of the technology. For general applications, such as for small pleasure craft, or scientific vehicles, the vane design is pretty much unchanged, the vane material is composed from mobile layers of flexible polymer, which contract when an alternating current is applied. These stacks of sheets form crude ‘muscles’ which are grouped in opposing pairs, with one of their ends attached to hull, the other to a flexible beam that juts from it. The movements from the ‘muscles’ can point the beam in different orientations, and this set up provides the basic elements for the propulsive vane, which is simply a line of such units. Other the whole assembly a flexible and robust polymer coat not only shields the individual parts, but also smooths out the shape creating an almost perfect hydrodynamic surface. Though this particular design may seem complicated, but in reality for a small craft there are perhaps only 10 or 20 elements in each vane, each with perhaps four muscle groups each, even a simple computer can handle this number of elements with ease, and a more complex one can optimise the use of these elements for any kind of manoeuvre. The disadvantage to this design is that there is a lifetime to the individual components, the muscle sets slowly degrade, and the beams can fail from fatigue, and although individual failures are not important for the entire propulsion system, they do need to be replaced. Maintenance for these vehicles requires the removal of the outer membrane, which would probably be replaced at the same time (more from biological adhesions than damage), which would then reveal the complex banks of muscles arranged around the driving beams. These units are simply swapped out with new parts. Although maintenance is straightforward it is often messy as the vane is often pumped with lubricant, the materials now used in the Federation have relatively broad lifetimes, and still operate under easy conditions (low voltage, liquid media and low strain), though degradation especially from continuous use.

            Though this design is commonplace other designs are widely used, often variants on the same theme, however there exists a completely different way of forming the hydrodynamic surface. Rather than making use of flexible polymers, the vanes and fins could be constructed from micromachines, which can continuously reassemble into new designs as the need requires. Movement of the surfaces is simply achieved by scaling the motions of the individual units in the whole structure. This technique is extremely advanced, and such ‘active hulls’ are only really required for extremely sophisticated applications. These methods also require much more power, and much more computer processing, though the later can be an integral part of the micro machine components. This kind of technology is allied to nanite nanotechnology though in this the component parts are only capable of movement and repositioning, and do not possess any processing capability, as such this kind of technology does not pose the risks with other nanotechnologies.